1. Technical Field
The present invention relates to a cylindrical sieve and a cylindrical sifter, and more specifically to a technique of sieving various granular materials and powdery materials with the cylindrical sieve.
2. Background Art
A conventionally known cylindrical sieve generally includes a cylindrical sieve screen having square meshes as shown in Patent Literatures 1 and 2, rectangular meshes as shown in Patent Literature 3, or special polygonal meshes according to the applications as shown in Patent Literature 4.
There is, however, difficulty in sieving various granular materials in different shapes, such as cylindrical grains. Inclusion of any powder or agglomerate significantly lowers the commercial value of the sieved granular material. The granular material should thus be sieved while keeping the granulated shape. For example, grains or granules (e.g., soup stock grains) included in a food product, such as instant noodle, are generally produced by extrusion as brittle, long, cylindrical grains. The granular material formed in a certain shape do not so easily pass through the apertures of the sieve body, compared with the powder material. Sieving the granular material accordingly has the problem of difficulty in passage through the screen and the problem of the lowered commercial value due to the potential destruction or cracking of the grains stuck between the screen and a stirring member rotating in the screen. The effective measure to solve such problems is thus highly demanded. Using a stirring member is not preferable since the granular material may be damaged (destroyed or cracked) by the contact with the stirring member.